1) In Princess Cookie, she visited the 캔디 Orphanage. Baby Snaps was still a kid there, and Bubblegum looked 18. It was the past. While Cookie has grown physically, PB still remains the same.
2) In the promo art for Burning Low, Flame Princess seems to very young, like 5 years old. While Peebles in 다음 to the lantern, looking 18 years old.
3) In The Suitor, the oldest suitor said he had been waiting for PB for 300 years. Indicating that she has lived for 300+ years. I think that it is because of 캔디 Biomass that makes her live.